I'm sorry if this sounded too negative; that's not my intent. This game as it is is already an awesome achievement, and I have no doubt that some of these concerns are already well-understood by Toady. The new subterranean features and more random creatures will certainly add to the necessity for situational gameplay.
To clarify a bit, however, it's seems to me important not to pile on difficulty for a young fortress unless the player has some idea that his/her own choices have generated that difficulty--in terms of site choice, world particulars, digging too deep, etc. For example, I wouldn't want to see farming become more complex for the early game, but wouldn't mind a bit to see extra challenges for it in the later game. Some of those 10+ year forts with 3000 prepared meals, for instance, could attract some monstrous vermin! Not to mention that nobles ought to be capable of more picky, luxurious culinary tastes than pioneering workaday dwarves. As always, ignoring these challenges should be feasible albeit with penalties, and there should be multiple solutions available to the clever player. (Which there usually are in DF!)
As far as "can I?" and "should I?", I'd be interested in seeing the creativity applied to the latter question generate situations that apply to the former. Take fort style, for example--let's say you build a 30 z-level execution tower. That manifests already in the code by the tracking of all those falling deaths, and that could have some influence on your dwarves' thoughts and behavior, subject to their personality. It could have influence on how other races view your fort--a Jainist-style nonviolent fort shouldn't prompt the same reactions from the various races as a blood-temple for the blood god.
Depending on the personalities of rulers and diplomats, that execution tower (and the accompanying engravings representing its use) could eventually lead to fun cycles of war and peace, given the ETHIC tags. It could even modify your site's biome, given all the out-and-out murder, and start attracting any nearby evil creatures to your fort.
Mostly I'm looking for the personal, creative uses of DF mechanics to generate core game problems of survival and fort happiness. Ideally, surmounting such mature fort challenges would require personal and creative use of the game mechanics--not just a simple formulaic approach. In one world a blood-soaked ziggurat of a fort might be necessary for intimidating a race's violent rulers into peace, whereas in another it might be counterproductive and -cause- wars. In a site neighboring (but not containing) an evil chasm, it might alter your biome's EVIL to the extent whole herds of wild trolls come to settle there.
Does this make any sense to anyone? :-P So much text...